I found the below page which is the most informative I have seen about the yellowing of plastic computer and console cases. After reading it im thinking of at a minimum rubbing uv protection compounds over my computers. Another idea is to paint them in clear uv resistant paint. If you have used hydrogen peroxide to bleach your computer cases (I think it may make them brittle, but anyway..) then you should clear coat them to stop them going yellow again. Both to block UV and to block oxygen. It seems both oxygen and light attack the plastic. The oxygen attacks worse I believe after a bleach job. If we do nothing and just let them yellow more they will become so brittle bits will start breaking off during maintenance etc. At some point I may try this uv clear coat idea on a case that is already damaged so ok to experiment on, to see if it makes it look too shiny or something.

- works best on plain white or cream cases. Care should be taken on coloured cases (e.g. breadbin C64) as it's easy to overcook and cause bloom.- I agree that oxygen exposure is probably just as important as light for re-yellowing (having had a number of computers re-yellow after treatment even though kept in near complete darkness).

After extensive reading of these bleach experiments I do not believe they are a good idea. When its bromide that has caused or accelerated the yellowing then bleaching just takes off the surface layer. Theres plenty more still in the plastic will will leach out again. It seems once you whiten the plastic you make the transfer of bromide happen even faster plus add a oxygen sensitivity to the mix. It seems the treatment gives the computer a oxygen allergy! I suggest if you totally cant stand a little yellowing then cover the treated plastic in a UV clear matte coating to block oxygen getting to the surface and to try to aid a little in reducing brittleness. Myself I will leave my yellowed computers and printers etc as they are. I really dont want to make that plastic brittle. I had one atari st case that had become so brittle with age that whatever I did new bits kept breaking off. Sad, the motherboard is ok so I will use it as games machine for my daughter to play with. Love that younger kids will give an older game a go and enjoy it.

After extensive reading of these bleach experiments I do not believe they are a good idea. When its bromide that has caused or accelerated the yellowing then bleaching just takes off the surface layer. Theres plenty more still in the plastic will will leach out again. It seems once you whiten the plastic you make the transfer of bromide happen even faster plus add a oxygen sensitivity to the mix. It seems the treatment gives the computer a oxygen allergy! I suggest if you totally cant stand a little yellowing then cover the treated plastic in a UV clear matte coating to block oxygen getting to the surface and to try to aid a little in reducing brittleness. Myself I will leave my yellowed computers and printers etc as they are. I really dont want to make that plastic brittle. I had one atari st case that had become so brittle with age that whatever I did new bits kept breaking off. Sad, the motherboard is ok so I will use it as games machine for my daughter to play with. Love that younger kids will give an older game a go and enjoy it.

My c64 is not yellow enough to bother me.

Its probably the best one ive ever seen.

If its a real rough yellow one, it would not bother me too much if i bleached it anyway, but I really want to find another c64 that i can use as I think this one is better left in its box in the dark.

There are UV protector products for plastic in cars etc, you can get these from repco and supercheap, it could be worth a try with these?They also can be cleaned off with isopropoyl alcohol easily enough.

I've found if cases are yellowed then damage has already taken place and the plastic is brittle anyway. In my experience the de-yellowing doesn't seem to increase brittleness. These are just my own observations though. I'd be interested in any valid research that shows de-yellowing treatments further damage plastics.

I've found if cases are yellowed then damage has already taken place and the plastic is brittle anyway. In my experience the de-yellowing doesn't seem to increase brittleness. These are just my own observations though. I'd be interested in any valid research that shows de-yellowing treatments further damage plastics.

Yes, very true.For the most part, its not a problem, and if the plastic is that far gone with yellowing, who really worries about it if you can make it look a darn sight better than before?

I was talking with an Amiga collector who is outside of the normal groups, and he mentioned that he sprayed on a clear UV protectant and the yellow didn't return. This peaked my interest too, so I'll have to find out exactly what product he tried and see if I can replicate.

SpidersWeb wrote:I was talking with an Amiga collector who is outside of the normal groups, and he mentioned that he sprayed on a clear UV protectant and the yellow didn't return. This peaked my interest too, so I'll have to find out exactly what product he tried and see if I can replicate.

Just wanted to post up to +1 the UV protectant idea.

Yes, I've heard that too but it seems that oxygen exposure plays a more significant role in re-yellowing than UV. At least in my experience. Some of my retrobrited units re-yellowed in closed boxes in a dark room where the only light was the faintest of glimmers through the cracks in the top of the box!